If you have spent time, money and hope raising plants under glass, there is nothing more disheartening than losing them to a single hard frost. A greenhouse buys you a few extra weeks at either end of the season, but on a cold British night the temperature inside can drop almost as low as it does outside. That is where a greenhouse heater earns its keep. Its main job is not to create a tropical paradise, but to hold the frost at bay and keep tender plants, overwintering fuchsias and early seedlings ticking over through the coldest months.
We have spent years heating our own greenhouses through damp Midlands winters, and we know that the right heater depends on your greenhouse size, whether you have a power supply out there, and how much you are prepared to spend running it. Below we round up the best greenhouse heaters you can buy in the UK this year, from tiny tubular heaters that sip electricity to powerful fan heaters that will keep a big glasshouse frost-free. There is honest advice on running costs, sizing and safety too, because a heater that is wrong for your space is money down the drain.
Quick verdict: our top greenhouse heaters at a glance
For most gardeners with a power supply to the greenhouse, an electric fan heater with a built-in thermostat is the sensible choice. It only fires up when the temperature drops, moves warm air around to prevent damp and cold spots, and needs almost no maintenance. The Bio Green Palma is our overall favourite for small to medium greenhouses, while the larger Bio Green Phoenix suits bigger glasshouses. If you have no electricity out there, a paraffin heater like the Parasene Compact is a dependable, off-grid backup. And if all you need is gentle, low-cost frost protection, a tubular heater is hard to beat.
How to choose a greenhouse heater
Power source: electric, paraffin or gas
This is the first decision, and it usually comes down to whether you have mains power in your greenhouse.
- Electric heaters are the cleanest and most controllable option. Paired with a thermostat they only run when needed, produce no fumes or moisture, and can be left alone for weeks. The catch is you need a proper outdoor-rated power supply, ideally installed by a qualified electrician on an RCD-protected circuit.
- Paraffin heaters need no electricity, making them the go-to for allotment greenhouses and sheds off the grid. They are cheap to buy and reassuringly simple, but they burn fuel that must be topped up, give off some fumes, and release water vapour that raises humidity. You will need to leave a vent slightly open.
- Gas heaters (usually bottled propane or butane) put out a lot of heat and, like paraffin, work without mains power. They suit larger greenhouses but share the same drawbacks around ventilation, moisture and the ongoing cost of refilling bottles.
Match the heater to your greenhouse size
An underpowered heater will struggle on the coldest nights, while an oversized one wastes money. As a rough guide, a small 6×4 or 6×6 greenhouse can be kept frost-free with a 1kW to 2kW electric heater or a single decent paraffin burner. A medium 8×6 greenhouse is comfortable with a 2kW to 2.5kW fan heater. Larger 8×10 or bigger glasshouses benefit from a 2.8kW to 3kW unit, or two smaller heaters placed at each end for even coverage. Bubble insulation on the inside of the glass dramatically cuts how much heat you need.
Running costs and thermostats
A thermostat is the single most important feature for keeping bills down. Without one, a 2kW heater running all night is eye-wateringly expensive. With one, the heater only clicks on when the temperature drops below your set point, which on a mild night might be barely at all. Set the thermostat as low as your plants will tolerate, usually just above freezing for frost protection at around 3 to 5 degrees, and insulate the greenhouse well. If your chosen heater lacks a built-in thermostat, a separate plug-in unit like the Bio Green Frostwatch is a worthwhile add-on.
The best greenhouse heaters for 2026
1. Bio Green Palma Basic 2.0kW Electric Fan Heater – best overall
The Bio Green Palma has become something of a default recommendation among UK greenhouse growers, and for good reason. It is a well-built electric fan heater with a stainless steel body designed to shrug off the damp, and it can run as a heater in winter or a cooling fan in summer. The Palma Basic comes with an analogue thermostat, so it only draws power when the temperature dips, and it circulates air nicely to prevent the stagnant, damp pockets that encourage mould. At 2kW it comfortably keeps a small to medium greenhouse frost-free.
Bio Green sell an upgraded version with a more precise digital thermostat if you want tighter control, but the Basic model does the essential job well and is the one most people should start with. It is not the cheapest fan heater on the shelf, but the build quality and reliability justify the extra outlay. Expect to pay around £120 to £160.
Pros:
- Robust, damp-resistant stainless steel construction built for greenhouse use
- Built-in thermostat keeps running costs sensible
- Doubles as a summer cooling fan
Cons:
- More expensive than generic fan heaters
- The Basic model’s analogue thermostat is less precise than the digital version
2. Bio Green Phoenix 2.8kW – best for large greenhouses
If your greenhouse is on the larger side, or you want to hold a warmer temperature for tender or exotic plants, the Bio Green Phoenix steps things up. Its 2.8kW output and accurate digital thermostat make it well suited to 8×8 glasshouses and above, and the digital display lets you dial in a precise target temperature to the degree. Like the Palma, it is built to cope with humidity and can be used as a fan through the warmer months.
It is a premium buy, but for anyone overwintering a collection of plants that will not forgive a cold snap, the extra capacity and control are worth having. Reckon on around £180 to £230 depending on where you shop.
Pros:
- Plenty of output for larger greenhouses
- Precise digital thermostat with clear display
- Well made and reliable, with good airflow
Cons:
- One of the pricier options here
- Overkill for a small 6×4 greenhouse
3. VonHaus 2000W Greenhouse Fan Heater – best mid-range value
For gardeners who want the convenience of an electric fan heater without the premium price, the VonHaus 2000W unit is a sensible middle ground. It offers two heat settings plus a cool-air fan setting, an adjustable thermostat and a carry handle, all in a compact, splash-resistant housing. It will keep a small to medium greenhouse ticking over nicely and is easy to move between the greenhouse and, say, a garage or workshop.
It is not built to the same industrial standard as the Bio Green models, so we would not expect it to last quite as many seasons in a very damp environment, but for the money it represents excellent value. Prices typically sit around £30 to £45.
Pros:
- Affordable and widely available
- Adjustable thermostat and multiple settings
- Compact and portable
Cons:
- Less rugged than premium greenhouse-specific heaters
- Thermostat is fairly basic
4. Warmlite 2000W Greenhouse Heater – best budget electric
At the truly budget end, the Warmlite greenhouse heater does the basics for very little money. It is a small 2kW fan heater with a couple of heat settings and a simple thermostat dial, ideal if you just need occasional frost protection in a small greenhouse and do not want to spend much. It is light and easy to stow away over summer.
The trade-off is a plasticky build and a thermostat that is more approximate than precise, so we would keep it for smaller spaces and lighter duties rather than relying on it through a brutal winter. Expect to pay around £25 to £35.
Pros:
- Very inexpensive
- Compact and lightweight
- Fine for occasional frost protection in a small greenhouse
Cons:
- Basic build quality
- Thermostat is imprecise
5. Greenhouse Tubular Heater – best for low-cost frost protection
Tubular heaters are the quiet workhorses of frost protection. These slim electric tubes, available in lengths that draw anywhere from around 45W up to 135W, sit low along the greenhouse floor and give off a gentle, steady warmth that rises up through the staging. Because they run at low wattage, they are cheap to run and can be left on through cold spells, or better still wired to a thermostat. For a small greenhouse a single tube often suffices; larger spaces may need two or more.
They will not blast out heat like a fan heater, so they are best thought of as background frost protection rather than a way to create real warmth. Individual tubes are inexpensive, usually around £20 to £35 each, and a thermostat is a worthwhile addition. Look for models from brands such as Hylite and Kingavon.
Pros:
- Low running costs thanks to modest wattage
- Gentle, even background heat with no moving parts
- Discreet and easy to mount along the greenhouse floor
Cons:
- Not powerful enough for rapid or serious heating
- Larger greenhouses need several tubes
6. Parasene Compact Paraffin Heater – best off-grid option
When there is no power at the greenhouse, a paraffin heater is the traditional answer, and the Parasene range is a long-standing favourite on British allotments. The compact model burns paraffin steadily to keep the chill off a small to medium greenhouse, needs no electricity, and is simplicity itself to use: fill it, light it, and it keeps going. It is a dependable insurance policy against frost when the forecast turns nasty.
The downsides are the ones common to all paraffin heaters. You have to keep it topped up with fuel, it produces some fumes and a fair amount of water vapour, so a little ventilation is essential, and there is an open flame to be sensible about. Kept clean and used properly, though, it is a reliable off-grid heater. Prices are usually around £40 to £55, plus the ongoing cost of paraffin.
Pros:
- No electricity needed, ideal for allotments and off-grid plots
- Simple, dependable and inexpensive to buy
- Good frost protection for small to medium greenhouses
Cons:
- Needs refuelling and produces fumes and moisture
- Requires ventilation and careful, sensible use around the open flame
Greenhouse heater comparison
| Heater | Type | Output | Best for | Approx price |
| Bio Green Palma Basic | Electric fan | 2.0kW | Small–medium greenhouses | £120–160 |
| Bio Green Phoenix | Electric fan | 2.8kW | Large greenhouses | £180–230 |
| VonHaus 2000W | Electric fan | 2.0kW | Mid-range value | £30–45 |
| Warmlite 2000W | Electric fan | 2.0kW | Budget frost protection | £25–35 |
| Tubular heater | Electric tube | 45–135W each | Low-cost background heat | £20–35 each |
| Parasene Compact | Paraffin | n/a | Off-grid greenhouses | £40–55 |
Getting the most from your greenhouse heater
A heater works far harder if the greenhouse is not helping it. Before winter really bites, line the inside of the glass with horticultural bubble insulation, which traps a layer of still air and can cut heat loss substantially. Check the door and vents close snugly and block any obvious draughts. Group tender plants together at one end so you can heat a smaller zone rather than the whole structure, and stand pots up off cold concrete on staging or a layer of fleece.
Keep the thermostat as low as your plants will accept. For most overwintering plants and hardy seedlings, simply staying a few degrees above freezing is enough, and every degree higher adds noticeably to the bill. On mild nights the heater may barely run at all, which is exactly what you want. Finally, a maximum-minimum thermometer is a cheap and genuinely useful companion, letting you see how cold it actually got overnight so you can fine-tune your settings.
Frequently asked questions
What temperature should I set my greenhouse heater to?
For frost protection, around 3 to 5 degrees Celsius is plenty for most plants and keeps running costs low. Tender or exotic plants may need a warmer minimum of 7 to 10 degrees. Set the thermostat to the lowest temperature your plants will tolerate.
Are electric greenhouse heaters expensive to run?
Only if they run constantly. With a thermostat and good insulation, an electric heater fires up just when the temperature drops, so on many nights it costs very little. Running a 2kW heater flat out all night, by contrast, is expensive, which is why the thermostat matters so much.
Can I use a normal household fan heater in my greenhouse?
It is not recommended. Ordinary indoor fan heaters are not built for the damp, humid conditions of a greenhouse and can be a safety risk. A purpose-made greenhouse heater has splash-resistant construction and is designed for the environment.
Do I need a heater for an unheated greenhouse in summer?
No. Heaters are for the cold months. In summer the challenge is keeping the greenhouse cool with shading and ventilation, though some fan heaters, like the Bio Green models, double up as cooling fans.
Final verdict
For the majority of UK gardeners with power to the greenhouse, an electric fan heater with a thermostat is the smart choice, and the Bio Green Palma Basic is our overall pick for small to medium greenhouses thanks to its build quality and sensible running costs. Step up to the Bio Green Phoenix for larger glasshouses, or save money with the VonHaus 2000W if you want fan-heater convenience on a budget. Where you only need gentle background warmth, a tubular heater is cheap to buy and run, and if there is no electricity out there, the Parasene Compact paraffin heater is a proven off-grid standby. Whichever you choose, pair it with good insulation and a low thermostat setting and your tender plants should sail through the winter.
For more on getting your growing space ready for the colder months, take a look at our guides to the best cold frames, garden fleece and greenhouse staging elsewhere on MyGreenShed.
